I'm getting a shipping container delivered to my property that weighs about 5000 pounds. Once it's delivered I will need to re-position it. I'm thinking of trying to use a number of cylindrical logs, together with some mechanical advantage to move it. My car has a towing capacity of 1500 pounds, so I'm contemplating getting a 6:1 block and tackle, effectively allowing my car to pull 10,000 pounds. I'm a little iffy on a few points though. What is the actual force that is required to pull a 5000 pound container over rolling logs on grass ( slope will also factor in) I have no idea what the coefficient of friction is here. Does the rope that feeds the pulley have to be able to withstand the full force or just 1/6 of the force? Assuming I need an anchor point, does the anchor point need to hold the full force of the pull? (any suggestions on how I can create an anchor point in a grass field .... was thinking maybe driving a steal pipe down a few feet at an angle). What else am I missing?
Your Cars towing capacity is considering towing on a highway where you have to be able to accelerate to traffic speed and decelerate safely. Considering you are only moving this off road you should be able to safely pull a load as heavy as you have traction for.If you have a tow hitch already on your vehicle the weakest point is likely to be the chain or cable you use. You will need to exercise extreme caution that should that fail there are no people in the danger zone.
With a block and tackle you distribute the load over the number of lines carrying the load. Easy way to look at it is if there are 3 ropes between the pulleys they share 1/3 the load each but if you have a single rope going from the pulley to the load or the pulling vehicle it will of course have the entire load.
How far are you needing to move this container? If it is more than a short distance you might want to consider paying someone to move it for you.